The purification of protein in cross-flow microfiltration of microbe/protein mixtures

The use of cross-flow microfiltration to purify BSA from yeast/BSA binary suspension is studied. The yeast cake properties, the BSA rejection coefficient and the filtration flux under various operating conditions, such as cross-flow velocity, filtration pressure and suspension pH value, are measured and discussed. The experimental results show that the filter cake plays the major role in determining the filtration resistance, the filtration flux as well as the BSA rejection. The filtration rate increases with the increase of cross-flow velocity, while decreases with the increase of filtration pressure or suspension pH. The BSA rejection coefficient is mainly determined by the sweeping effect on the cake surface and the cake mass. An increase in cross-flow velocity, filtration pressure or suspension pH, causes the BSA rejection coefficient to be higher. Theoretical models are derived to predict the filtration flux and the BSA rejection coefficient at the pseudo-steady state under various conditions. The calculated results agree fairly well with experimental data. On the viewpoint of protein recovery and protein purification flux, pH 3.0, high cross-flow velocity and low filtration pressure is the optimum operating condition for purification of BSA from the binary suspension using cross-flow microfiltration